Least number which becomes prime or 0 or 4 after n-1 iterations of f(x) = sum of prime factors of x (cf. A001414). Agrees with A048133 except for the second term.
a(21) <= 536226160966. a(22) <= 2681130804805. a(23) <= 8512643845707. - Donovan Johnson
Table of n, a(n) for n=1..20.
Cf. A002217, A001414, A048133.
Sequence in context: A102735 A088960 A263528 * A199928 A047688 A089925
Adjacent sequences: A121357 A121358 A121359 * A121361 A121362 A121363
Klaus Brockhaus, Jul 27 2006
Edited comment and a(19)-a(20) from Donovan Johnson, Oct 16 2010